The following description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
When driving lasers, control circuits frequently need to adjust the input in order to compensate for changes in the environment. U.S. Pat. No. 6,031,660 to Park teaches a pump laser diode that detects an optical excitation signal from a pump laser diode and outputs an electrical signal to a controller for the pump laser diode. The current controller compares the current level of the electrical signal received from the photodiode with a level preset by a user, and adjusts the intensity of the electrical signal on the basis of the comparison result. Presetting the bias in accordance with a user input, however, requires a great deal of experimentation time and effort for each laser diode, which can hamper production efficiency.
U.S. Pat. No. 9,083,468 to Zheng teaches a system that accesses a look up table that stores calibration data for drive currents and associated optical wavelengths generated by a laser diode. Zheng's system could apply drive currents or equivalent temperature control voltages associated with an optical wavelength to achieve the idealized wavelength. Zheng's system, however, requires a time-consuming and expensive process to derive calibrated drive currents for each optical wavelength.
U.S. Pat. No. 9,083,467 to Ide teaches a controller that switches an optical mode of a transmitter in response to a measured temperature. Ide's controller measures the temperature of a module and switches the mode when the temperature passes a threshold level. However, if there is a malfunction in the laser diode itself, Ide's controller might switch the mode in a manner to try to correct for an error that is uncorrectable by merely switching the optical mode of the transmitter, which may damages the laser.
Thus, there is still a need for systems and methods for inexpensively driving a laser diode that prevents system failure If a feedback signal is impaired.